The present invention relates to a method and a corresponding device for adaptive control of separation distance and/or driving speed of a motor vehicle. Control systems of the specific type are, for example, also known as adaptive cruise control systems (ACC systems).
An ACC system based on radar is known from SAE Technical Paper Series 961010, International Congress and Exposition, Detroit, Feb. 26-29, 1996, xe2x80x9cAdaptive Cruise Control Systemxe2x80x94and Development Trendsxe2x80x9d, Winner, Witte, Uhler, Lichtenberg, Robert Bosch GmbH. In this version, the multi-purpose enabled radar sensor is mounted at the front end of a motor vehicle for determining separation distances from, and relative speeds to vehicles driving ahead. The data ascertained from the radar system are conducted to a control unit via a bus system. On the basis of the transmitted radar data and the driver input, the control unit determines an appropriate acceleration requirement, which, in turn, is transmitted to a longitudinal control unit. The longitudinal control unit activates activators depending on the acceleration requirement of the control unit. These actuators can be the motor vehicle engine, the clutch, or the motor vehicle brakes. Activation of the actuators results in such specific motor vehicle performance characteristics, which, in turn, are fed back to the control unit, thus forming a control loop. Depending on which acceleration requirement is involved, either the drive train or the brakes is/are activated. In making this selection, the gradient of the road is taken into consideration. In addition, the boundary properties, or rather the physical limitations of the drive train must be known or calculated accordingly.
A method for adaptive control of separation distances and/or driving speeds of a motor vehicle, at least in a first operational mode, an engine (14) of the motor vehicle and, in a second operational mode, a brake (14) of the motor vehicle being able to be activated as a function of a quantity (aSoll) (aSetpoint), representing an acceleration, is further refined in that the quantity (aSoll) representing the setpoint acceleration is formed and/or limited at least as a function of at least one basic value (aBaseMax, aBaseMin). A preferred embodiment provides that the change over time of the magnitude (aSoll) representing the setpoint acceleration can be limited in a positive and in a negative direction as a function of determinable boundary values (aMinus, aPlus), it being further advantageous that, during the restriction of the magnitude (aSoll), representing the characteristic acceleration, the cycle time (dt) of a control device (10) and/or a regulator (13) are taken into consideration. (aMinus and aPlus represent time derivatives of accelerations, which is not immediately recognizable in the illustration used in this text).
The method according to the present invention prevents xe2x80x9cvehicle judderxe2x80x9d quite effectively during the activation of the engine control and the brake (subsystems, in this case). By adding/subtracting a certain amount to/from the basic values, one achieves a jerk-free change in acceleration. Here, a jerk is understood to mean the change in time of the acceleration. It is especially advantageous that external and internal acceleration requirements can be converted by selecting base values to this effect. In the same manner, for instance, hystereses and non-settable ranges in the subsystems can be realized by defining base values, without the need for costly/additional special treatment for these operating states.
A device for adaptive control of separation distance and/or driving speed of a motor vehicle is developed further, compared to the related art, in that the means for carrying out the abovementioned method is provided.